Method of manufacturing semiconductor device and apparatus for processing substrate

ABSTRACT

A process for producing a semiconductor device, in which in the formation of a boron doped silicon film from, for example, monosilane and boron trichloride by vacuum CVD technique, there can be produced a film excelling in inter-batch homogeneity with respect to the growth rate and concentration of a dopant element, such as boron. The process includes the step of performing the first purge through conducting at least once of while a substrate after treatment is housed in a reaction furnace, vacuuming of the reaction furnace and inert gas supply thereto and the steps of performing the second purge through conducting at least once of after carrying of the substrate after treatment out of the reaction furnace, prior to carrying of a substrate to be next treated into the reaction furnace and while at least no product substrate is housed in the reaction furnace, vacuuming of the reaction furnace and inert gas supply thereto.

TECHNICAL FIELD

The present invention relates to a method of manufacturing asemiconductor device.

BACKGROUND ART

In a process of manufacturing the semiconductor device such as IC andLSI, there is performed the fact that a thin film is formed on asubstrate by a reduced pressure CVD method (Chemical Vapor Depositionmethod). As one of such film forming methods, there is implemented thefact that a silicon film having been doped with boron is formed by thereduced pressure CVD method. Hitherto, in order to dope the boron to thesilicon film, there has been used diborane. In this case, by introducinga gas from a furnace body lower part under a state that, in a reactionfurnace, plural wafers have been stack-supported vertically in a boat tothereby cause the gas to vertically ascend, if there is used a reducedpressure CVD apparatus which forms the thin film on the wafer by a heatCVD method while using that gas, in-face homogeneities of a filmthickness and a resistivity have been as bad as 10-20% in whole regionsfrom a bottom region (lower part region) to a top region (upper partregion) in the CVD apparatus.

There is known the fact that the above film thickness in-facehomogeneity is greatly improved by using boron trichloride instead ofthe diborane and there is obtained such a boron-doped polycrystallinesilicon film that its film thickness in-face homogeneity is 1% or lessin the whole regions (refer to Patent Document 1).

Patent Document 1: JP-A-2003-178992

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

However, in the case where the film having been doped with the boron isformed by using the boron trichloride for the silicon, if there is aninterval between a film formation run (film formation batch processing)and a next film formation run, there is a problem that a B (boron)concentration and a growth rate decrease in the next film formation runand, in this case, it has been necessary that, in the next filmformation run, the film formation run is once implemented without aproduct being put in and thereafter the film formation run isimplemented with the product being continuously put in.

However, if the film formation run is once implemented without theproduct being put in, an efficiency of a product processing becomes badand, even if the run is implemented taking a time, the B concentrationand the growth rate are not necessarily obtained with a goodreproducibility.

An object of the invention exists in providing a method of manufacturinga semiconductor device, in which, in such a case that the boron-dopedsilicon film is formed by the reduced pressure CVD method by usingmonocilane and the boron trichloride for instance, it is possible toproduce a film whose inter-batch homogeneities of a concentration and agrowth rate of an element doped like the boron for instance are good.

Means for Solving the Problems

In order to solve the above problems, a 1st characteristic of theinvention exists in a method of manufacturing a semiconductor device,comprising the steps of: loading a substrate into a reaction furnace,performing in the reaction furnace a processing to the substrate,performing, under a state that the substrate after the processing hasbeen accommodated in the reaction furnace, a 1st purge by performing anevacuation and a supply of an inert gas to the reaction furnace by morethan at least one time, unloading the substrate after the processing outof the reaction furnace, and performing, after the substrate after theprocessing has been unloaded out of the furnace, before a substrate tobe processed next is loaded into the reaction furnace, and under a statethat at least a product wafer is not accommodated in the reactionfurnace, a 2nd purge by performing the evacuation and the supply of theinert gas to the reaction furnace by more than at least one time,wherein a pressure change quantity in the reaction furnace per unit timein the 2nd purge step has been made larger than a pressure changequantity in the reaction furnace per unit time in the 1st purge step.

Desirably, the pressure change quantity in the reaction furnace per unittime in the 2nd purge step is made larger than 30 Pa/second and 500Pa/second or smaller. Further, desirably, in a method of manufacturing asemiconductor device according to claim 1, a difference between amaximum pressure and a minimum pressure in the reaction furnace in the2nd purge step is made larger than a difference between a maximumpressure and a minimum pressure in the reaction furnace in the 1st purgestep. Further, desirably, in the 1st purge step and the 2nd purge step,the evacuation and the supply of the inert gas are repeated by pluraltimes, and a cycle of the evacuation and the supply of the inert gas inthe 2nd purge step is made shorter than a cycle of the evacuation andthe supply of the inert gas in the 1st purge step. Further, desirably,in the 1st purge step and the 2nd purge step, the evacuation and thesupply of the inert gas are repeated by plural times, and a cycle numberof the evacuation and the supply of the inert gas in the 2nd purge stepis made more than a cycle number of the evacuation and the supply of theinert gas in the 1st purge step. Further, desirably, in the 1st purgestep and the 2nd purge step, the evacuation and the supply of the inertgas are repeated by plural times, in the 1st purge step there issupplied the inert gas into the reaction furnace under a state that anexhaust valve, which has been provided in an exhaust line for exhaustingan inside of the reaction furnace, has been opened, and in the 2nd purgestep there is supplied the inert gas into the reaction furnace under astate that the exhaust valve has been closed. Further, desirably, the1st purge step is performed under a state that a support, which hassupported the substrate, has been accommodated in the reaction furnace,and the 2nd purge step is performed under a state that a support, whichdoes not support at least a product substrate, has been accommodated inthe reaction furnace. Further, desirably, the 1st purge step isperformed under a state that a support, which has supported thesubstrate, has been accommodated in the reaction furnace, and the 2ndpurge step is performed under a state that a support, which hassupported a dummy substrate without supporting a product substrate, hasbeen accommodated in the reaction furnace. Further, desirably, in thesubstrate processing step there is used a gas containing boron. Further,desirably, in the substrate processing step there is formed aboron-doped silicon film on the substrate. Further, desirably, in thesubstrate processing step there are used monocilane (SiH₄) and borontrichloride (BCl₃). Further, desirably, the 2nd purge step is performedeach time in every time the processing to the substrate is performed.

A 2nd characteristic of the invention exists in a method ofmanufacturing a semiconductor device, comprising the steps of: charginga substrate to a support, loading the support having been charged withthe substrate into a reaction furnace, performing in the reactionfurnace a processing to the substrate, unloading the support, which hassupported the substrate after the processing, from the reaction furnace,discharging, after the support has been unloaded, the substrate afterthe processing from the support, loading, after the substrate after theprocessing has been discharged, the support into the reaction furnacewithout charging at least a product substrate to the support, andperforming a purge by performing, under a state that the support notcharged with at least the product substrate has been accommodated in thereaction furnace, an evacuation and a supply of an inert gas to thereaction furnace by more than at least one time without introducing areactive gas into the reaction furnace.

Desirably, the purge step is performed under a state that a dummysubstrate has been supported without supporting the product substrate tothe support. Further, desirably, the purge step is performed each timein every time the processing to the substrate is performed. Further,desirably, a pressure change quantity in the reaction furnace per unittime in the purge step is made larger than 30 Pa/second and 500Pa/second or smaller.

In the 2nd purge step or the purge step, there suffices if an FCP (FastCycle Purge) is used. The FCP is a method of strongly purging an insideof the reaction furnace by generating a sharp pressure fluctuation byopening/closing a main valve in a short cycle in the reaction furnace ofthe reduced pressure CVD apparatus. If this FCP is used, it is possibleto remove, e.g., boron having adhered to inside of the reaction furnace,a boat, a dummy wafer and the like to thereby uniformize an in-furnacestate before a film formation and, by this, it is possible to suppressfluctuations of a boron concentration and a growth rate after the filmformation.

A 3rd characteristic of the invention exists an apparatus for processinga substrate, comprising: a reaction furnace for processing thesubstrate, a gas supply line for supplying a gas into the reactionfurnace, a loading/unloading device for transporting the substrate intoand from the reaction furnace, and a controller which controls so as toperform, under a state that the substrate after the processing has beenaccommodated in the reaction furnace, a 1st purge by performing anevacuation and a supply of an inert gas to the reaction furnace by morethan at least one time, which controls so as to perform, after thesubstrate after the processing has been unloaded out of the reactionfurnace, before a substrate to be processed next is loaded into thereaction furnace, and under a state that at least a product substrate isnot accommodated in the reaction furnace, a 2nd purge by performing theevacuation and the supply of the inert gas to the reaction furnace bymore than at least one time, and additionally which controls such that apressure change quantity in the reaction furnace per unit time in the2nd purge is made larger than a pressure change quantity in the reactionfurnace per unit time in the 1st purge.

In the substrate processing apparatus of the invention, it is possibleto implement various methods having been mentioned above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an apparatus for processing asubstrate according to an implementation mode of the invention.

FIG. 2 is a flowchart showing film formation procedures in a method ofmanufacturing a semiconductor device according to the implementationmode of the invention.

FIG. 3 is a flowchart showing FCP procedures in the method ofmanufacturing the semiconductor device according to the implementationmode of the invention.

FIG. 4 is a diagram showing a change in a B concentration in continuousthree runs in an embodiment according to the invention.

FIG. 5 is a diagram showing inter-batch idling time dependencies of theB concentration in the embodiment according to the invention and acomparison example.

FIG. 6 is a diagram showing a change in a growth rate in the continuousthree runs in the embodiment according to the invention.

FIG. 7 is a diagram showing inter-batch idling time dependencies of thegrowth rate in the embodiment according to the invention and thecomparison example.

FIG. 8 is a diagram in which a normal cycle purge and an FCP have beencompared in the method of manufacturing the semiconductor deviceaccording to the implementation mode of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an implementation mode of the invention is explained on the basisof the drawings.

As a preliminary consideration before the invention is made, a cause ofa boron concentration fluctuation between batches is considered asfollows. That is, since a desorption quantity, of boron before the filmformation, from a reaction furnace inner wall face, a boat surface andthe like becomes different by an idling time between the batches, thereis considered the fact that a boron quantity doped at a film formationtime changes and thus the boron concentration fluctuates.

Further, there is considered the fact that, in the presentimplementation mode since a film growth occurs by a catalyst effect ofthe boron, the growth rate fluctuates by the fact that the boronconcentration fluctuates. In order that the desorption quantity, of theboron before the growth, from the reaction furnace inner wall face, theboat surface and the like is made as constant as possible, it isconsidered to flow the boron trichlodide in a certain constant quantityinto the furnace before the film formation, or to oxidation-coat afurnace inside before the film formation. However, in the former thereis an anxiety that the boron segregates in an interface between thesubstrate and the film, and in the latter there is an anxiety that acleaning is hindered by the wall face having been oxidized at anin-furnace gas cleaning time, so that both cannot be said a desirablepolicy. Whereupon, as a result of earnest studies, the present inventorhas found out a strong purge method called an FCP (Fast Cycle Purge)capable of solving these problems. It has been understood that, byalways performing this FCP before the film formation, the desorption ofthe boron from the reaction furnace inner wall face, the boat surfaceand the like is promoted, and the desorption quantity, of the boronbefore the film formation, from the reaction furnace inner wall face,the boat surface and the like can be stabilized, so that it is possibleto improve a stability of the boron concentration and the growth ratebetween the batches.

The implementation mode of the invention is one having been made on thebasis of the consideration like this.

In FIG. 1, there is shown a structural, schematic view of a batch systemlongitudinal type reduced pressure CVD apparatus of a hot wall system asan apparatus for processing a substrate of the invention. This reducedpressure CVD apparatus is one in which the monocilane (SiH₄) and theboron trichloride (BCl₃) are used as a reaction gas and, by introducingthe gas from the furnace body lower part under the state that, in thereaction furnace, plural wafers have been vertically stack-supported inthe boat as a support to thereby cause the gas to vertically ascend,there is formed a boron-doped silicon thin film, i.e., a boron-dopedamorphous silicon thin film or a boron-doped polycrystalline siliconthin film, on the wafer by the heat CVD method while using that gas.

In an inside of heaters 6 a-6 d having been separated to four zones,which constitute a hot wall furnace and heat a wafer 4 as the substrate,there are installed a quartz-made reaction pipe that is an outer casingof a reaction furnace 12, i.e., outer tube 1, and an inner tube 2 insidethe outer tube 1 with their axes being made vertical. There is adaptedsuch that between the tubes of these two kinds can be evacuated by usinga mechanical booster pump 7 and a dry pump 8. Accordingly, the reactiongas introduced to an inside of the inner tube 2 vertically ascends theinside of the inner tube 2, descends between the tubes of the two kinds,and is exhausted. A quartz-made boat 3 in which the plural wafers 4 havebeen vertically stack-charged with their centers being aligned isinstalled in the inner tube 2. When the wafer 4 has been exposed to thereaction gas, the thin film is formed on the wafer 4 by reactions in agas phase and in a wafer 4 surface. Incidentally, a heat insulationplate 5 having been charged in a region, of the boat 3, lower than aregion in which the wafers 4 have been charged is one for homogenizing atemperature in a position range in which the wafers 4 exist. Further, inFIG. 1, 10 is a boat rotation shaft, and it is connected to a rotationmechanism 17. Further, 11 is a stainless-made lid (seal cap), and it isconnected to a boat elevator 18 as a transporting-in/out device(ascent/descent device). There is adapted such that the boat 3, therotation shaft 10, the lid 11 and the rotation mechanism 17 aremonolithically ascended/descended by this boat elevator 18, and the boat3 is loaded into or unloaded from the reaction furnace 12. The lid 11closely adheres to a stainless-made furnace mouth manifold 15 supportingthe outer tube 1 and the inner tube 2 through an O-ring 11 a as a sealmember, thereby sealing an inside of the reaction furnace 12. Further,there is adapted such that the boat 3 is rotated in the reaction furnace12 by the rotation mechanism 17 through the rotation shaft 10.

Incidentally, in the boat 3, slots each of which supports the wafer 4are provided by 172. For example, the slots up to 10th counted from thelowermost slot constitute a lower dummy region D1, and the dummy wafer 4is supported by the slot belonging to this lower dummy region D1.Further, for example, the slots from 11th to 167th constitute a productwafer region P, and the product wafer 4 is supported by the slotbelonging to this product wafer region P. Further, for example, theslots from 168th to 172nd constitute an upper dummy region D2, and thedummy wafer 4 is supported by the slot belonging to this upper dummyregion D2. Incidentally, below the wafer arrangement regions (D2, P, D1)of the boat 3, there are provided plural slots supporting the pluralheat insulation plates 5, and the heat insulation plate 5 is disposed inan underside than the heater 6 d corresponding to an L zone amonglater-mentioned heater zones having been divided into four. Further, inFIG. 1, a top region T, a center region C, and a bottom region B denoterespectively a region in which there exist the product wafers 4 of theslots from 129th to 167th, a region in which there exist the productwafers 4 of the slots from 37th to 128th, and a region in which thereexist the product wafers 4 of the slots from 11th to 36th. Further,among the heater zones having been divided into four, the lowermost L(Lower) zone (corresponding to the heater 6 d) corresponds to a region,in an underside than the 1st slot, in which the wafer scarcely exists, aCL (Center Lower) zone (corresponding to the heater 6 c) of the secondfrom below corresponds to a region in which the dummy wafer 4 and theproduct wafer 4 of the slots from 2nd to 56th coexist, a CU (CenterUpper) zone (corresponding to the heater 6 b) of the third from below,i.e., the second from above, corresponds to a region in which theproduct wafer 4 and the dummy wafer 4 of the slots from 57th to 172ndcoexist, and an uppermost, i.e., the fourth from below, U (Upper) zone(corresponding to the heater 6 a) corresponds to a region, in an upsidethan the last-mentioned region, in which no wafer exists.

A nozzle (straight nozzle) 13 made of quartz for instance, whichsupplies a monocilane gas (SiH₄), is provided in the furnace mouthmanifold 15 below a region opposite to the heaters and below thereaction pipe. As to a nozzle 14 made of quartz for instance, whichsupplies a boron trichloride gas (BCl₃), ones whose lengths differ areinstalled in the reaction furnace 12 by plural pieces, it is possible tomidway-supply the boron trichloride from plural places, and it ispossible to control a partial pressure of the boron trichloride gas(BCl₃) in each place in the reaction furnace 10. That is, there isconstituted such that the quartz nozzle 14 supplying the borontrichloride gas (BCl₃) is provided by plural pieces, here five pieces intotal, among them one nozzle (straight nozzle 14 a) is provided,together with the nozzle 13 supplying the monocilane gas (SiH₄), in thefurnace mouth manifold 15 below the region opposite to the heaters andbelow the reaction pipe, and other four nozzles (L-shaped nozzles) 14 bpass through the above furnace mouth manifold and their respective jetports are provided respectively in the same interval so as to correspondto the 30th slot, the 70th slot, the 110th slot and the 150th slot,thereby being capable of midway-supplying the boron trichloride fromplural places in a vertical direction within the reaction furnace 10.

Incidentally, as to the straight nozzle 13 supplying the monocilane gas(SiH₄) and the straight nozzle 14 a supplying the boron trichloride gas(BCl₃), there is constituted such that their respective jet ports areopened toward a direction parallel to a wafer surface, i.e., ahorizontal direction, thereby jetting the respective gases toward thedirection parallel to the wafer surface, i.e., the horizontal direction.Further, there is constituted such that gas jet ports of the pluralL-shaped nozzles 14 b supplying the boron trichloride gas (BCl₃) areopened toward a direction perpendicular to the wafer surface, i.e., avertically upward direction, thereby jetting the gas toward thedirection perpendicular to the wafer surface, i.e., the verticaldirection.

Further, the nozzle 13 is connected to a gas line 20. This gas line 20is bifurcated, and one of this bifurcated gas line is connected to amonocilane gas (SiH₄) source 23 through a mass flow controller 21 as aflow rate control means and a valve 22. Further, the other of thebifurcated gas line 20 is connected to a nitrogen gas (N₂) source 26through a mass flow controller 24 as the flow rate control means and avalve 25. The five nozzles 14 are connected to gas lines 27 having beenseparated into five. This gas line 27 is connected to a borontrichloride gas (BCl₃) source 30 through a mass flow controller 28 asthe flow rate control means and a valve 29.

The above-mentioned mechanical booster pump 7 and dry pump 8 areprovided in an exhaust pipe 16 whose one end has been connected to thefurnace mouth manifold 15. Additionally, in this exhaust pipe 16 thereis provided a main valve 9. For this main valve 9 there is used an APC(automatic pressure control) valve, and there is adapted such that itsopening is automatically adjusted such that a pressure in the reactionfurnace 12 becomes a predetermined value.

Incidentally, a controller 31 as a control means controls heatingtemperatures of the heaters 6 a-6 d, an open/close of the main valve 9,drives of the mechanical booster pump 7 and the dry pump 8, a drive ofthe boat elevator 18, a drive of the rotation mechanism 17, openings ofthe mass flow controllers 21, 24, 28, an open/close of each of thevalves 22, 25, 29, and the like.

Next, as one process in processes of manufacturing the semiconductordevice by using the above substrate processing apparatus, there isexplained about a film formation method which forms the boron-dopedsilicon film on the substrate. Film formation procedures are shown inFIG. 2. Incidentally, in the following explanations, an operation ofeach part constituting the substrate processing apparatus is controlledby the controller 31. After the inside of the reaction furnace 12 hasbeen first stabilized to a film formation temperature in a step S10, theboat 3 having been charged with the wafers 4 is loaded (inserted) intothe reaction furnace 12 in a step S12. Next, in a step S14, the insideof the reactor (reaction furnace 12) is exhausted and, in a next stepS16, an N₂ purge is performed in order to desorb a moisture and the likewhich have been adsorbed to the boat 3 and the tubes 1, 2. After anin-reactor (reaction furnace 12) leak check has been performed in a nextstep S18, flow rates of the monocilane and the boron trichloride are setin a next step S20 and a pressure is stabilized with the gases beingflowed into the reaction furnace 12 and, in a next step S22, on thewafer 4 there is performed a film formation of the boron-doped siliconfilm, i.e., the boron-doped amorphous silicon film or the boron-dopedpolycrystalline silicon film. If the film formation has terminated, in anext step S24, an inside of the reaction pipe and an inside of a pipingare cycle-purged by N₂ (1st purge step).

This 1st purge step is a normal cycle purge (Normal Cycle Purge:hereafter mentioned as NCP), and implements the cycle purge only by asupply and a stop of the N₂ gas by opening and closing the valve 25having been mentioned above with the main valve 9 being opened intact.After the NCP has been implemented by three—several cycles for instancein the step S24, it proceeds to a step S26. Purge conditions of the NCPare as follows for instance.

-   -   Time per one cycle: 4-6 min    -   Evacuating time per one cycle: 2-3 min    -   N₂ supply time per one cycle: 2-3 min    -   Total time: 12-18 min    -   Minimum pressure (reach pressure when evacuating): 0.05-1 Pa    -   Maximum pressure (reach pressure when supplying N₂): 20-100 Pa    -   Cycle number: 3-several times    -   N₂ supply quantity: 0.5-1 slm    -   Pressure change quantity per unit time: 7 Pa/second or less

In a next step S26, the inside of the reactor is returned up to anatmospheric pressure by the N₂. If having returned to the atmosphericpressure, the boat 3 is unloaded in a next step S28, and the wafers 4are naturally cooled in a next step S30. Finally, the wafers 4 are takenout of the boat 3 in a step S32.

Next, there is explained about a method of purging the inside of thereaction furnace after a film formation termination by the FCP. FCPprocedures are shown in FIG. 3. After the film formation having beenshown in FIG. 2 has terminated, in a step S34, the boat 3 not chargedwith the product wafers is loaded (inserted) into the reaction furnace12 again. In this case, the dummy wafer may be removed from the boat 3,or may be being charged in the boat 3. Next in a step S36, theevacuation is started by driving the mechanical booster pump 7 and thedry pump 8. If the pressure in the inside of the reactor (reactionfurnace 12) has become a predetermined value, e.g., about 1.0 kPa, in anext step S38 the main valve 9 is opened instantaneously, therebyperforming the exhaust. In a next step S40, the main valve 9 is closedand, in a next step S42, the N₂ gas is introduced again into the reactor(reaction furnace 12). In a next step S44, it is judged whether or not acycle of the steps S38-S42 has reached to a predetermined value, e.g.,100 times and, in a case where it does not reach to the predeterminedvalue, it returns to the step S38 and this cycle is repeated till itreaches to the predetermined value. In a case where the steps of thesteps S38-s42 have reached the predetermined value, it proceeds to anext step S46. In the step S46, the N₂ is introduced into the reactionfurnace 12 till the pressure in the reaction furnace 12 becomes theatmospheric pressure. In a next step S48, the boat 3 not charged withthe product wafers is unloaded and, in a case where the boat 3 has beencharged with the dummy wafers, the dummy wafers are cooled in a nextstep S50 and, in a next step S52, there is started a next batch, i.e.,the film formation having been shown in FIG. 2.

Incidentally, desirable purge conditions of the FCP are as follows.

-   -   Time per one cycle: 0.5-2 min    -   Evacuating time per one cycle: 0.25-1 min    -   N₂ supply time per one cycle: 0.25-1 min    -   Total time: 20-100 min    -   Minimum pressure (reach pressure when evacuating): 0.05-1 Pa    -   Maximum pressure (reach pressure when supplying N₂): 1000-1200        Pa    -   Cycle number: 10-200 times    -   N₂ supply quantity: 0.5-1 slm    -   Pressure change quantity per unit time: 30 Pa/second-500        Pa/second, desirably 100 Pa/second-500 Pa/second

Incidentally, if the pressure change quantity per unit time exceeds 500Pa/second, loads on the reaction furnace and the pump become large, sothat it is difficult to implement in regard to an interlock of thesubstrate processing apparatus.

Like this, in comparison with the normal cycle purge, the FCP ischaracterized in that the pressure change quantity per unit time is verylarge (rapid).

In FIG. 8 there is shown a graph indicating the pressure changequantities in the reaction furnace, with respect to a time elapse, ofthe FCP having been shown in the steps S38-S44 and the NCP having beenshown in the step S24 while being compared. An abscissa of the graphindicates the time elapse (second), and an ordinate the pressure (Pa) inthe reaction furnace, respectively. In the drawing, M. V. OPEN, N2 STOPmeans an operation stopping the supply of the N2 under a state that themain valve has been opened in the FCP, and it is shown by a circle inwhich a hatching has been applied. Further, in the drawing, M. V. CLOSE,N2 IN means an operation supplying the N2 under a state that the mainvalve has been closed, and it is shown by a white circle. Further, inthe drawing, N2 STOP means an operation stopping the supply of the N2 inthe NCP, and it is shown by a black reverse triangle. Further, in thedrawing, N2 IN means an operation stopping the supply of the N2 in theNCP, and it is shown by a white reverse triangle. Further, a solid lineindicates the pressure change in the FCP, and a dotted line the pressurechange in the NCP, respectively. As mentioned above, the FCP performsthe cycle purge by opening/closing the main valve (M. V.). On the otherhand, the NCP performs the cycle purge by the supply/stop of the N₂ withthe main valve being opened intact.

As understood also from FIG. 8, in the FCP, the pressure change quantityin the reaction furnace per unit time is large in comparison with theNCP. For example, in the NCP the pressure change quantity per unit timeis in the order of 7 Pa/second in maximum, whereas in the FCP it is inthe order of 500 Pa/second in maximum. Further, in the FCP a difference(pressure fluctuation width) between a maximum pressure and a minimumpressure is large in comparison with the NPC. For example, the pressurefluctuation width is 1000-1200 Pa in the FCP, whereas it is in the orderof 20-100 Pa in the NCP. Further, in the FCP a cycle number is many incomparison with the NCP. For example, the cycle number is 10-200 timesin the FCP, whereas it is 3-several times in the NCP.

As having been mentioned above, in comparison with the NCP, in the FCPsince the pressure change quantity per unit time in the reaction furnaceis large (the pressure change quantity per unit time of the FCP is 4-70times or more of the NCP), a gas flow rate passing through the inside ofthe reaction furnace per unit time, i.e., a gas flow rate contributingto the purge, becomes large as well, so that a purge effect isoverwelmingly large.

Especially, in the case where there is performed the process using theboron trichloride (BCl₃), if there is made so as to perform only theNCP, the BCl₃ exists abundantly in a form liable to desorb in a regionextending from a bottom region B whose temperature is comparatively lowto the furnace mouth part. The BCl₃ having been left like this becomesHCl on the occasion of the boat unloading and becomes a cause ofcorroding the furnace mouth part (the stainless-made manifold, the sealcap and the like), thereby exerting an influence on the growth rate ofthe boron-doped silicon film or the like in the next film formation run.That is, especially in the case where the process using the borontrichloride (BCl₃) is performed, a sufficient purge effect is notobtained by the NCP. Whereupon, in the above implementation mode, thereis made so as to perform a strong purge called the FCP. By this, it ispossible to sufficiently remove the BCl₃ liable to remain in the abovelow temperature part, and thus it is possible to make such that noinfluence is exerted on the substrate processing in the next filmformation run.

Next, there are explained about an embodiment and a comparison example.

Embodiment

The boron-doped silicon thin film was formed by using theabove-mentioned reduced pressure CVD apparatus and using the monocilane(SiH₄) and the boron trichloride (BCl₃) as the reaction gases. Everytime the film formation processing was performed, the FCP wasimplemented.

The film formation processing was implemented with a total pressure inthe reaction furnace 12 being made 66.5 Pa, an SiH₄ flow rate 0.2 slm, aBCl₃ flow rate 0.002 slm, and an in-furnace temperature 380-400° C.

The FCP was implemented with the maximum pressure (reach pressure whensupplying N₂) being made 1200 Pa, the minimum pressure (reach pressurewhen evacuating) 0.1 Pa, the time per one cycle 1 min, a time duringwhich the pressure is fluctuated from the maximum pressure to theminimum pressure 5 seconds, the cycle number 100 times, the total time100 min, and an N2 supply quantity 1 slm.

Comparison Example

The film formation processing was performed similarly to the embodiment,and the FCP was not implemented.

In FIG. 4, there is shown a batch (run) frequency dependency of a Bconcentration in the embodiment, i.e., a result having measured theboron (B) concentration in a continues 3-run about the product waferhaving been mounted to the slot (#89) in the center region. There couldbe confirmed the fact that a fluctuation of the B concentration fell toless than 2% by implementing the FCP.

In FIG. 5, there are shown inter-batch idle time dependencies of the Bconcentration in the embodiment and the comparison example. In thecomparison example (the FCP does not exist), the B concentration sharplydecreases in an idling of 2-6 hours, and its dispersion is about ±4%with the B concentration after a 24-hour idling being included as well.In contrast to this, in the embodiment (the FCP exists), a Bconcentration change falls to less than ±2% even after the 24-houridling. From the results of FIG. 4 and FIG. 5, the fact is understoodthat, by implementing the FCP, it is possible to improve an inter-batchhomogeneity of the B concentration.

In FIG. 6, there is shown a batch (run) frequency dependency of thegrowth rate of the boron-doped silicon thin film in the embodiment,i.e., results having measured changes in the growth rate in thecontinuous 3-run about the product wafers having been mounted to theslot (#167) in the top region and to the slot (#11) in the bottomregion. There could be confirmed the fact that, by implementing the FCP,a fluctuation of the growth rate fell to less than 2%.

In FIG. 7, there are shown inter-batch idle time dependencies of thegrowth rate of the boron-doped silicon thin film in the embodiment andthe comparison example. In the comparison example (the FCP does notexist), the growth rate more largely disperses by the inter-batch idletime, whereas in the embodiment (the FCP exists) the fluctuation of thegrowth rate scarcely exists even after the 24-hour idling, additionallyeven after a 38-hour idling. From the results of FIG. 6 and FIG. 7, thefact is understood that, by implementing the FCP, it is possible toimprove an inter-batch homogeneity of the growth rate.

As having mentioned above, the FCP is liable to desorb the BCl₃ and a Clcomponent, which have adhered to the constitutional members in thereaction furnace, i.e., the boat, the dummy wafer, and additionallyinner walls etc. of the reaction pipe, the manifold and the seal cap.Its reason is because, in the FCP since the N₂ is accumulated in thereaction furnace up to a high pressure and pulled instantaneously, thepressure change per unit time is large and a purge gas quantity becomesabundant as well, so that the purge effect becomes overwelmingly large.

Incidentally, although in the above implementation mode and embodimentthere has been shown one having been applied to the reduced pressure CVDapparatus, the invention is not one limited this, and it can begenerally applied to an apparatus using a gas containing the boron (B)with a boron dope diffusion apparatus being included, and can be appliedalso about an apparatus using a gas containing phosphorous (P), such asPH₃ for instance, other than the boron, a gas containing arsenic (As)such as AsH₃, and the like.

Like the above, although the invention is characterized by matters setforth in claims, additionally there are included implementation modeslike the followings.

(1) An apparatus for processing a substrate, characterized by having areaction furnace for processing the substrate, a supply means forsupplying a processing gas into the reaction furnace, atransporting-in/out device for transporting the substrate into and fromthe reaction furnace, and a control means which controls so as torepeat—after the substrate has been transported out of the reactionfurnace by the transporting-in/out device, before a substrate to beprocessed next is transported-in, and under a state that at least aproduct substrate does not exist in the reaction furnace—an evacuationand a supply of an inert gas with respect to the reaction furnace.

(2) An apparatus for processing a substrate, characterized by having aboat for charging the substrate, a reaction furnace for processing thesubstrate, a supply means for supplying a processing gas into thereaction furnace, a transporting-in/out device for transporting the boatinto and from the reaction furnace, and a control means which controlsso as to perform—after the boat has been transported out of the reactionfurnace together with the substrate by the transporting-in/out device,before a substrate to be processed next is transported-in, and under astate that an empty boat not charged with at least a product substratehas been inserted into the reaction furnace—an evacuation and a supplyof an inert gas with respect to the reaction furnace by more than atleast one time.

INDUSTRIAL APPLICABILITY

The invention can be utilized in a method of manufacturing asemiconductor device, which has a process of processing a substrate.

1. A method of manufacturing a semiconductor device, comprising thesteps of: loading a substrate into a reaction furnace, processing thesubstrate in the reaction furnace, performing a 1^(st) purge in a stateof the processed substrate in the reaction furnace by evacuating aninside of the reaction furnace through an exhaust line, supplying aninert gas into the reaction furnace, thereby changing a pressure in thereaction furnace, unloading the processed substrate from the reactionfurnace, and performing, after the processed substrate is unloaded fromthe reaction furnace and before another substrate is loaded into thereaction furnace, a 2nd purge by evacuating the inside of the reactionfurnace through the exhaust line, supplying the inert gas into thereaction furnace, thereby changing the pressure in the reaction furnace,wherein an amount of change in the pressure in the reaction furnace inthe 2^(nd) purge step is larger than an amount of change in the pressurein the reaction furnace in the 1^(st) purge step; and in the 1^(st)purge and in the 2^(nd) purge, the evacuation of the inside of thereaction furnace and the supply of the inert gas into the reactionfurnace are repeated two or more times; and in the 1^(st) purge, theevacuation of the inside of the reaction furnace and the supply of theinert gas into the reaction furnace are performed under a state that anexhaust valve, which is provided in the exhaust line, is open; and inthe 2^(nd) purge, the evacuation of the inside of the reaction furnaceis performed under the state that the exhaust valve is open and thesupply of the inert gas into the reaction furnace is performed under astate that the exhaust valve is closed.
 2. A method of manufacturing asemiconductor device according to claim 1, wherein a difference betweena maximum pressure and a minimum pressure in the reaction furnace in the2nd purge is larger than a difference between a maximum pressure and aminimum pressure in the reaction furnace in the 1st purge.
 3. A methodof manufacturing a semiconductor device according to claim 1, a cycle ofthe evacuation of the inside of the reaction furnace and the supply ofthe inert gas into the reaction furnace in the 2nd purge is shorter thana cycle of the evacuation of the inside of the reaction furnace and thesupply of the inert gas into the reaction furnace in the 1st purge.
 4. Amethod of manufacturing a semiconductor device according to claim 1,wherein a cycle number of the evacuation of the inside of the reactionfurnace and the supply of the inert gas into the reaction furnace in the2nd purge is greater than a cycle number of the evacuation of the insideof the reaction furnace and the supply of the inert gas into thereaction furnace in the 1st purge.
 5. A method of manufacturing asemiconductor device according to claim 1, wherein in the substrateprocessing step a gas containing boron is used.
 6. A method ofmanufacturing a semiconductor device according to claim 1, wherein inthe substrate processing step a boron-doped silicon film is formed onthe substrate.
 7. A method of manufacturing a semiconductor deviceaccording to claim 1, wherein in the substrate processing stepmonosilane (SiH₄) and boron trichloride (BCl₃) are used.
 8. A method ofmanufacturing a semiconductor device according to claim 1, wherein the2nd purge step is performed each time in every time the processing tothe substrate is performed.
 9. A method of manufacturing a semiconductordevice, comprising the steps of: charging a substrate to a support,loading the support charged with the substrate into a reaction furnace,processing the substrate in the reaction furnace, unloading the support,which supports the processed substrate from the reaction furnace,discharging the processed substrate from the support after the supportwhich supports the processed substrate is unloaded from the reactionfurnace, loading the support into the reaction furnace without charginga product substrate to the support, after the discharging the processedsubstrate from the support, and purging, under a state that the supportnot charged with the product substrate has been accommodated in thereaction furnace, by evacuating an inside of the reaction furnacethrough an exhaust line, supplying an inert gas into the reactionfurnace, thereby changing a pressure in the reaction furnace, wherein,in the purging step, the evacuation of the inside of the reactionfurnace and the supply of the inert gas into the reaction furnace arerepeated two or more times, and, the evacuation of the inside of thereaction furnace is performed under a state that an exhaust valve, whichis provided in the exhaust line, is open, and the supply of the inertgas into the reaction furnace is performed under a state that theexhaust valve is closed.
 10. A method of manufacturing a semiconductordevice according to claim 9, wherein the purging step is performed undera state that a dummy substrate is supported without supporting theproduct substrate to the support.
 11. A method of manufacturing asemiconductor device according to claim 9, wherein the purge step isperformed each time in every time the processing to the substrate isperformed.